Scientists have discovered a “lost world” of unknown creatures in a remote rainforest perched on a giant boulder plateau in Queensland, Australia.

In an expedition bearing parallels to Arthur Conan Doyle’s classic novel, the team of biologists found three unidentified reptile species living on the upland plateau, which is accessible only by helicopter because of a “monstrous wall” of “millions of giant, piled up boulders the size of houses and cars”.

The team, led by Dr Conrad Hoskin, from James Cook University, and Dr Tim Laman, from Harvard University, encountered a “bizarre” looking leaf-tailed gecko, a golden-coloured skink and a boulder-dwelling frog species during a four-day trek to Cape Melville.

It is believed that the species have been isolated from their closest cousins for millions of years. “We’re talking about animals that are ancient – they would have been around in the rainforest of Gondwana … rainforest that’s been there for all time,” said Dr Hoskin. “This [gecko] was mind-blowing, completely bizarre. It’s really big, around eight inches with long spindly legs and huge eyes.”

Patrick Couper, curator of Reptiles and Frogs at the Queensland Museum, and collaborator on the gecko’s description, said the newly-named Cape Melville Leaf-tailed Gecko was the “strangest new species to come across my desk in 26 years working as a professional herpetologist”. Dr Hoskin had known of the range, which is around nine miles long and three wide, for more than a decade. But his interest was reignited when the advent of Google Earth allowed him to view it from above.

He said he was planning to return, having explored only about a tenth of the area during the four-day journey. “If we find a mammal that would be incredible,” he said.